Our research covers six different areas related to the cellular evolution characteristic of primary melanomas and to the formal histogenetic precursors of malignant melanoma. These six areas of investigation are: (1) natural language access to the computerized data base of all of the melanomas studied prospectively by the Pigmented Lesion Study Group of the University of Pennsylvania; (2) studies of dysplastic nevi, the important histogenetic precursors of melanoma, in familial and sporadic melanoma; (3) fine-structural studies of primary melanomas, dysplastic nevi, normal nevi and Spitz tumors; (4) studies of the phenotypic characterizations of cells cultured from normal nevi, dysplastic nevi and melanomas; (5) a variety of studies with antimelanoma monoclonal antibodies emphasizing their use with immunoperoxidase methods to detect melanoma-associated antigens in intact human tumors; (6) studies of lymphocyte subsets in the host response to melanocytic neoplasms.